Distributed caching cluster client configuration

ABSTRACT

A cache or other cluster is configuration-aware such that initialization and changes to the underlying structure of the cluster can be dynamically updated for use by a client. A client may use a client driver as an intermediary that is responsible for managing the communication with the cluster. For example, a client driver may resolve an alias from a static configuration endpoint to a storage node. The client driver may request an initial configuration from the storage node and then update configuration from one or more storage nodes that store current configuration of the cluster.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/685,607, filed Nov. 26, 2012, entitled “DISTRIBUTED CACHING CLUSTERCLIENT CONFIGURATION”, which is related to co-pending U.S. patentapplication Ser. No. 13/685,596, filed Nov. 26, 2012, entitled“DISTRIBUTED CACHING CLUSTER CONFIGURATION”, co-pending U.S. patentapplication Ser. No. 13/685,615, filed Nov. 26, 2012, entitled“DISTRIBUTED CACHING CLUSTER MANAGEMENT”, and co-pending U.S. patentapplication Ser. No. 13/685,620, filed Nov. 26, 2012, entitled“REPLICATION IN DISTRIBUTED CACHING CLUSTER”, the contents of which areherein incorporated in their entirety.

BACKGROUND

Data centers provide computing resources for use by one or more clients.These services may include computing, storage and networking services.For example, a data center may provide a machine to host an application,storage to store application data, cache to quickly respond to repeateddata requests and networking to enable communication between resources.By making use of the data center services, a customer may pay forcomputing and/or resource use rather than purchasing anticipatedhardware needs. This enables a customer to expand and contract use ofcomputing services according to demand. For example, an application maybe configured to request more storage as needed rather than a developeror administrator monitoring and anticipating use.

On demand systems may be used to reduce the number of times a databasemust be read by caching data and objects from the database. For example,one implementation uses a client centered architecture where a clientknows the servers, but the servers are not known to each other. To reador set a key, the client uses a hash to determine which server tocontact and contacts that server. The server then calculates a secondhash to determine where to store or read the corresponding value.Additions or subtractions to the group of servers are managed by theclient.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments in accordance with the present disclosure will bedescribed with reference to the drawings, in which:

FIG. 1 shows an illustrative example of a cache cluster environment inaccordance with at least one embodiment;

FIG. 2 shows an illustrative example of a cluster caching management inaccordance with at least one embodiment;

FIG. 3 shows an illustrative example of an environment in accordancewith at least one embodiment;

FIG. 4 shows an illustrative example of an embodiment of cluster cachingmanagement;

FIG. 5 shows an illustrative example of logical connections betweencomponents in accordance with at least one embodiment;

FIG. 6 shows an illustrative chart of a process in accordance with atleast one embodiment;

FIG. 7 shows an illustrative example of a process in accordance with atleast one embodiment;

FIG. 8 shows an illustrative example of a process in accordance with atleast one embodiment;

FIG. 9 shows an illustrative example of a process in accordance with atleast one embodiment;

FIG. 10 shows an illustrative example of a process in accordance with atleast one embodiment; and

FIG. 11 shows an illustrative example of hashing in accordance with atleast one embodiment;

FIG. 12 shows an illustrative example of hashing in accordance with atleast one embodiment; and

FIG. 13 illustrates an environment in which various embodiments can beimplemented.

DETAILED DESCRIPTION

In the following description, various embodiments will be described. Forpurposes of explanation, specific configurations and details are setforth in order to provide a thorough understanding of the embodiments.However, it will also be apparent to one skilled in the art that theembodiments may be practiced without the specific details. Furthermore,well-known features may be omitted or simplified in order not to obscurethe embodiment being described.

Techniques described and suggested herein include enabling a clientdriver to connect to a cache cluster such that initialization andchanges to the underlying structure of the cache cluster can bedynamically updated while remaining transparent to a client using theclient driver. For example, a client may connect to a cache clusterthrough use of a client driver to manage requests for cached data andchanges to the cache cluster. The cache cluster may comprise a set ofone or more memory caching nodes that each includes a reserved memoryspace that stores a configuration of the cache cluster. A configurationmay be an indication of, among other things, the number of memorycaching nodes in the cache cluster and the location of the memorycaching nodes. The client driver may follow a protocol to request cacheddata, such as using a key to access a value of a key-value pair, frommemory caching nodes in the cache cluster. The protocol, such as amemcached protocol, may be further extended to include operations on thereserved memory space that stores the configuration. These operationsmay include create, read, update and destroy operations related to theconfiguration. In addition, the operations may also include metadataoperations that describe the configuration, such as versioning, a changelog or configuration history operations. Using the protocol and/orprotocol extensions, a client may request a current configuration from amemory caching node. The client may then use the configuration todetermine which keys may be stored and/or retrieved from which memorycaching nodes, such as a key space definition. The client mayperiodically (or aperiodically) retrieve an updated configuration from amemory caching node and update the key space definition.

The client may use a consistent hashing algorithm to distribute keysamong the memory caching nodes and form a key space based on theconfiguration received. In one embodiment, a memory caching node isassigned one or more angles or points along a circle. The assignment ofangles or points along the circle may be determined by multiple factors,including size of the memory caching node, frequency of requests forkeys in the assigned portion of the key space and other factors. Ahashing algorithm may be used to determine where a key falls along thecircle. The point or angle where the key falls may then be traced in apredefined direction (e.g., clockwise) around the circle until a firstmemory caching node assignment is encountered. The first memory cachingnode assignment encountered determines which memory caching nodeservices the key. By using a consistent hashing algorithm, such asdescribed, cache invalidation may be minimized and caching nodeplacement may be targeted. Furthermore, if each node is allowed toservice multiple points or angles, a load of a lost memory caching nodemay be distributed among multiple remaining memory caching nodes if eachassigned point or angle of a lost memory caching node is followed by anassignment of a different memory caching node.

In some embodiments, the client, via a client driver, may be responsiblefor managing the cache cluster. A client may request deletion,replacement and/or addition of memory caching nodes to the cachecluster. New nodes added to the cluster may be given one or moreassignments of the available key space. In some embodiments, thisassignment may include replicating a portion of a key space assigned toanother memory caching node. The new node may then be added to aconfiguration and sent to be stored in some or all of the memory cachingnodes in the cache cluster.

In one embodiment, initialization of a client driver may occur bycontacting a configuration endpoint provided in an initialconfiguration. The client driver may resolve an alias of the staticconfiguration endpoint to a memory caching node in a cache cluster. Anexample of a configuration endpoint may be a static hostname thatresolves to an active memory caching node through domain name services.The client may request initial configuration from the memory cachingnode and then update configuration from distributed memory caching nodesthat store current configuration of the cache cluster.

In one illustrative example, a cache cluster has four memory cachingnodes servicing a web application making requests to a database. Becauseof heavy traffic, a fifth memory caching node may be brought on line toaid in the caching of data requests from the web application to thedatabase. After bringing the memory caching node online, a managementsystem may update the configuration for the cache cluster to incorporatethe fifth memory caching node. The updated configuration may be pushedto one or more of the memory caching nodes for storage and retrieval. Ifneeded, a static configuration endpoint may receive an update to analias referencing a memory caching node that comprises the updatedconfiguration. Clients of the cache cluster may receive the alias fromthe configuration endpoint and receive the updated configuration tominimize caching disturbances. A client driver may retrieve and use thenew configuration to determine the updated key space such that theclient driver has access to the fifth memory caching node.

A cache cluster may cache data and object to reduce accesses to a datasource. The cache cluster may include one or more memory caching nodes.Each node may store a portion of a set of cached data. The cached datamay be split between memory caching nodes based on keys that are used toretrieve an element of data from the cache cluster. Data sources mayinclude a database, application programming interface (API) or otherdata store or data source. The memory caching nodes may use computermemory as storage for cache, such as RAM, to speed up responses torequests.

Configurations may be delivered to a client in a plurality of ways. Inone embodiment, a pre-defined configuration endpoint can be queried by aclient driver to resolve an address for a memory caching node from whichto request a current configuration. The configuration endpoint may bestatically declared such that support software, including a clientdriver for the client system may be able to resolve an alias provided bythe configuration endpoint to a memory caching node from which aconfiguration may be obtained. The configuration can describe how toaccess caching resources of the cache cluster, including the memorycaching nodes. This static declaration of an alias allows for newclients to start and self-configure to current cache cluster conditionsrather than manually configure a new client before starting the newclient. In another embodiment, the memory caching nodes can also containreserved space for storing configuration describing the structure of thecache cluster. While normal caching of data can cause data to expire, asection of storage may be partitioned such that configuration may bestored in such reserved configuration space without worry of deletion.This internal configuration stored by a memory caching node allows aclient already in communication with a memory caching node to alsorequest a current configuration, if newer than the current configurationof the client. By providing the current configuration, memory cachingnodes may be altered with the expectation that clients will update uponaccess of a memory caching node. This delivery of new configuration to aclient already in communication with a memory caching node may bethrough methods that include periodic polling of a memory caching nodeby a client driver or push notification by a memory caching node to aclient driver.

The term provisioning is meant to be read broadly to include theassignment of a computing resource to a use. In some embodiments, thisincludes preparing the computing resource for use. In one embodiment, aprovisioning of a memory caching node would include the assignment of aserver, installation of an operating system, installation andconfiguration of the memory caching node and enabling the memory cachingnode for use. For example, a provisioning system may select a server touse as a memory caching node. The provisioning system may then create aworkflow that prepares the server for use as a memory caching node. Aspart of the workflow, a machine image may be loaded on the server. Themachine image may include operation system, memory caching softwareand/or settings. After loading the machine image, the server may becaused to boot into the operating system and receive any furthersoftware and/or settings. Such settings may include cache clusterconfiguration. After provisioning is complete, the server may be turnedover to a management system for use as a memory caching node.

Turning now to FIG. 1, an illustrative example of a cache clusterenvironment 100 in accordance with at least one embodiment is shown. Aclient system 114 may use a cache cluster 113 to provide a betterresponse time for cached requests than could be available by directlyaccessing a data store. This caching may also reduce a load of a datastore. A client system 114 may include an application that requires datafrom the cache cluster 113. A client driver 104, such as an importedclient code library, may be used to manage communication between theapplication 102 and the cache cluster 113. The client driver may helpensure proper communication with the cache cluster 113 by periodicallychecking for new configuration 108 information from one or more memorycaching nodes 110 in the cache cluster 113. By checking and, if needed,loading configuration 108 from a memory caching node 110, the clientdriver 104 can allow for a dynamic and/or changing configuration 108 ofthe cache cluster 113, such as the provisioning of more memory cachingnodes 110 in the cache cluster 113. The client driver 104 may also makethe changes in the communication with the cache cluster 113 withoutnotifying the application 102. In one embodiment, application requestsare paused while the client driver 104 updates configuration 108.Application requests then resume after the client driver 104 finishesloading the configuration 108. Thus, the application 102 may be blind tochanges in the cache cluster 113 because of the operation of the clientdriver 104.

The memory caching nodes 110 may form a cache cluster 113. A cachecluster 113 may include one or more memory caching nodes 110 that storecached data in a cache 112. The cache cluster 113 may also be enabled tobe cluster aware of memory caching nodes 110 by tracking configurationchanges and updating configuration 108. It should be recognized that thecomputing resources, programs and processes referenced herein may be runon actual hardware, virtual machines or combinations thereof. A memorycaching node 110 storing the configuration 108 may be referenced by astatic alias of a configuration endpoint. The configuration endpoint 106may thus serve as reliable resource in which to find a memory cachingnode 110 to contact and retrieve configuration 108 information. Inaddition, one or more of the memory caching nodes 110 may includeconfiguration storage to store current configuration 108 of the cachecluster 113. This configuration storage allows a client driver 104 toretrieve configuration 108 from memory caching node 110, even if thememory caching node 110 referenced by the configuration endpoint 106 isreplaced.

In one embodiment, the client driver 104 resolves a memory caching node110 from information given by the configuration endpoint 106. The clientdriver 104 may retrieve an initial configuration 108 from the resolvedmemory caching node 110. The client driver 104 loads this configuration108 and then proceeds to service requests from the client and direct therequests to the proper memory caching nodes 110. Periodically or uponnotification, the client driver 104 may retrieve updated configurationinformation 108 from the memory caching nodes 110. For example, thisupdated configuration information may include information about newprovisioned memory caching nodes 110 that are available. The clientdriver 104 may use this updated information to route requests to thememory caching nodes 110 according to the new configuration 108.

A configuration endpoint 106 may also be provided to aid inconfiguration 108 retrieval. In some embodiments, a configurationendpoint 106 is a static resource that may be directly referenced as analias to a memory caching node 110 for configuration 108 retrieval. Forexample, new clients may be initialized with a hostname of theconfiguration endpoint 106. Upon instantiation of a new client 114, theclient 114 may connect with the configuration endpoint 106 using clientdriver 104 to resolve an alias to a memory caching node 102 and retrievethe configuration 108 from the memory caching node 102. By providing theconfiguration endpoint 106, clients 114 may self-configure rather thanstart with a list of memory caching nodes 110 that may become obsoleteand require maintenance. In some embodiments, a client driver 104 maycontinue to retrieve a more current configuration 108 by requesting theconfiguration 108 from a memory caching node referenced in the aliasprovided by the configuration endpoint 106 or a memory caching node 110.In one embodiment the configuration endpoint is implemented by domainname system (DNS) services. A client may request a static hostname fromthe domain name server and receive an IP address that resolves to amemory caching node.

Turning now to FIG. 2, an illustrative example of a distributed memorycaching system 200 in accordance with at least one embodiment is shown.A client system 203 uses a client driver 204 to retrieve informationfrom a cache cluster 213 managed by a management system 214. In theembodiment shown, a client system 203 includes an application 202 thatretrieves data from the cache cluster 213. The client system 203 uses aclient driver 204 to manage the interface between the application 202and the cache cluster 213. For example, the application 202 may be ashopping website and the client driver 204 may be a library that exposesthe caching functionality through function calls and/or an applicationprogramming interface (API).

The client driver 204 may manage the communication with the cachecluster 213. In one embodiment, the client driver 204 supports automaticconfiguration. An initial configuration of the client driver 204 may besmall, such as a hostname of a configuration endpoint 206 that providesan alias at which configuration 208 may be obtained. In one embodiment,the alias is provided as part of the configuration endpoint acting as adomain name server. The configuration 208 may include information neededfor the client driver 204 to connect to and use the cache cluster 213.For example, an application 202 may provide a hostname and/or address ofa configuration endpoint 206 to the client driver 204 as part ofinitializing the client driver 204. Using the given hostname and/oraddress, the client driver 204 contacts the configuration endpoint 206to resolve an alias to a memory caching node 210 and requests aconfiguration 208 from the memory caching node 210. In one embodiment,this configuration is stored in a reserved memory space of the memorycaching node 210 that is not subject to certain cache rules of aprotocol implemented by the cache node (such as the memcached protocoland variations thereof), such as eviction. Information in the reservedmemory space may be accessed according to an extension to a standardcaching protocol, such as memcached. Upon receiving the configuration208, the client driver 204 may load the configuration 208. Once loaded,the client driver 204 may verify the configuration 208. In oneembodiment, the client driver 204 contacts one or more memory cachingnodes 210 and verifies the version of the configuration 208 against aconfiguration version contained in a second memory caching node 210. Theclient driver 204 may use the most recent configuration 208 discovered.The client driver 204 may then act upon requests for data from theapplication 202 by requesting the data from one or more memory cachingnodes 210 that store the data in their cache 212. Periodically, theclient driver 204 may check the loaded configuration version againstconfiguration versions stored by the memory caching nodes 210. Theclient driver 204 may elect to use the newest configuration discovered,which may be the current version loaded in the client driver 204. Byloading the configuration 208, the client driver can react to dynamicchanges in the cache cluster 213. For example, the configuration 208 mayidentify memory caching nodes 210 that are added or removed from thecache cluster 213. By loading the configuration, the client driver 204may react to any changes in the cache cluster 213 infrastructure withoutinstruction from the application 202.

Loading the configuration may synchronize, with other computing systems,a client driver's information about the cache cluster. In oneembodiment, several client drivers 204 exist at the same time to servemultiple instances of a web application, each on its own server.Synchronizing a configuration of the cache cluster 213 allows eachclient driver 204 to properly populate and request information frommemory caching node 210 that form the cache cluster 213. For examples ofpopulating and cache requests of memory caching nodes, see FIGS. 11-12and the associated description.

The client driver 204 and caching nodes 210 may communicate using astandard protocol, such as a memcached protocol, and extensions to theprotocol. For example, caching operations may use the standard protocol,while configuration operations may use extensions to the protocol, suchas additions to a command set of the protocol. In some embodiments, theextension operations operable on the reserved configuration storage mayinclude create, retrieve, update and destroy operations. Other extensionoperations may include a get configuration version operation, othermetadata manipulation operations and a propagate configuration request.

A management system 214 may be one or more computing resourcesresponsible for management of other systems. In FIG. 2, the managementsystem 214 is responsible for the distributed memory caching system 200,including the provisioning and monitoring of memory caching nodes 210 inthe cache cluster 213. The management system 214 may also receiveinstructions from customers and/or administrators such that themanagement of the management system 214 fits the needs of the customerand/or administrator. For example, a management system 214 may beresponsible for a set of memory caching nodes 210 that form the cachecluster 213. The management system 214, through a provisioning system asan example, may cause new memory caching nodes 210 to be instantiated orcurrent memory caching nodes 210 to be stopped. The management system214 may also be responsible for monitoring the cache cluster 213, whichmay include monitoring the set of memory caching nodes 210 forindicators. The indicators may include usage, failure or otherinformation about the use and/or underlying systems. A configurationendpoint 206 may also be maintained by the management system 214 toensure that an alias to an active memory caching node 210 that canprovide configuration 208 is always available.

In one embodiment, the management system 214 may use a monitoring systemand react to perceived problems with the caching service 200. Forexample, if a failure occurs in a failed memory caching node 210, thefailed memory caching node may be de-provisioned and removed from thecache cluster 213. A new memory caching node 210 may be provisioned toreplace the failed memory caching node and recover from loss of thefailed memory caching node. In other examples, the failed memory cachingnode may be repaired by replacing, reinitializing and recovering thememory caching node. Using the changes made to the cache cluster 213,the management system 214 may update the configuration 208 and cause theupdated configuration 208 to be stored in each memory caching node 210.If needed, the alias provided by the configuration endpoint 206 may alsobe updated. In another example, the management system 214 provisions anew memory caching node 210 due to an increase in demand for cacheddata. The management system 214 may update the configuration 208 withthe connection information to the new memory caching node 210 and causethe configuration 208 to be stored in memory caching nodes 210.

A configuration may include information necessary to connect to thecache cluster 213. In some embodiments that use a direct connectingconfiguration, this may include information to directly connect to eachmemory caching node 210. In other embodiments using a request forwardingconfiguration, the configuration 208 may identify a memory caching node210 responsible for the forwarding of requests to a memory caching node210 that holds the data in cache 212. In one embodiment, a hybridapproach may be taken where direct connection and request forwarding areboth available.

Turning now to FIG. 3, an illustrative example of a distributed memorycaching environment 300 in accordance with at least one embodiment isshown. The client application 309 (202 in FIG. 2), management system 312(214 in FIG. 2) and configuration endpoint 308 (206 in FIG. 2) may existin the context of a data center. The computers may be divided intotrusted computing resources within the data center 304 and untrustedexternal computing systems 316, 318, 320, sometimes referred to asapplication clients 322, outside the data center 304. Inside the datacenter 304, computing resources and networking 306 may be under thedomain and control of known administrators and thus have trustedinternal connections. Outside of the data center 304 may be beyond thecontrol of administrators, and therefore untrusted, such as the Internet305.

Inside the data center 304 may be memory caching nodes 302, internalnetworking 306, a management system 312, a gateway 310, a configurationendpoint 308 and a client application 309. An memory caching node 302may be connected to other memory caching nodes 302 through internalnetworking 306. The memory caching nodes 302 may also be connected witha management system 312. The management system 312 may receive requeststo manipulate computing resources, including provisioning resources andchanging routing. The memory caching nodes 302 and management system 312may also be connected with a gateway 310. The gateway 310 may filter androute external traffic to a client application 309, such as HTTP trafficto Web servers. For example, a client application 309 may communicatewith external systems 316, 318, 320, but memory caching nodes 302 arenot allowed external communications.

Outside the data center 304 may be any of a number of differentcomponents or environments, and may include the Internet 305 and variousexternal computing systems such as desktops 316, laptops 318 and mobiledevices 320, such as electronic book readers, mobile phones, tabletcomputing devices, etc. The systems 316, 318, 320 may be viewed asuntrusted because the systems 316, 318, 320 may not be administered by atrusted administrator. Further, the communication channels, such as theInternet, are not controlled by a trusted administrator. Thus, a messagefrom an external computing system 316, 318, 320 may be intercepted,counterfeited and/or exploited.

In some cases, and for protective reasons, client applications 309 on asecure internal network 306 may only be given the Internet 305 accessrequired to operate, if any at all. For example, a Web server in a datacenter 304 may only receive outside traffic on port 80 because a gateway310 provides access controls to the secure internal network that preventall other Internet 305 traffic from directly reaching the Web server. Inanother example, a memory caching node 302 on a secure internal network306 may not be connected to the Internet 305 because it is only queriedby a local Web server over the secure internal network. In otherembodiments, a client application 309 may be behind a load balancer,which may occasionally direct Internet 305 requests to the clientapplication 309.

Turning now to FIG. 4, an illustrative example of a distributed memorycaching management environment 400 in accordance with at least oneembodiment is shown. A management system 416 may monitor and/or managememory caching node 402. Memory caching node 402 may manage cachedkey-value pairs 410, respond to requests to provide cached values (fromthe key-value pairs 410) and provide a configuration 412 identifying howto communicate with the cache cluster 413 and/or each memory cachingnode 402. Key value pairs 410 may be inserted into a cache of the memorycaching node 402 when read and/or changed from a data store 408. Thecache cluster 413 allows potentially quicker responses to frequentlyaccessed and/or high access cost data than requesting data directly fromthe data store 408.

A memory caching node 402 may be provided that includes cache space 404and reserved memory space 406. The memory caching node 402 may beserviced by virtual and/or physical hardware, including a virtualmachine. The memory caching node may receive key/values pairs 410 tostore within the cache space 404. The key-values 410 may have anexpiration time, as well as early expiration depending on whether thememory caching node 402 runs out of cache space 404. The memory cachingnode 402 may use an algorithm to determine which key-value pairs 410 maybe expired early. In some embodiments, a least-frequently used algorithmis used to determine which items are expired early when a cache is full.In other embodiments, a cost of querying the data store may be factoredin. In one embodiment, the expiration may be based on which key-valuepairs 410 are not expected to be frequently accessed in the future. Thememory caching node 402 may also provide storage for a configuration 412detailing communication parameters with the cache cluster 413. In someembodiments, this configuration 412 may be stored in a reserved memoryspace 406 that is not subject to expiration. In one embodiment, theconfiguration 412 is stored in the cache space 404, but a client ormanagement system 416 ensures frequent enough requests and/or updates toensure the configuration 412 is available. The configuration 412 may beoverwritten and/or updated to keep current with changes to the cachecluster 413.

A configuration endpoint 414 may also be provided to aid inconfiguration 412 retrieval. In some embodiments, a configurationendpoint 414 is a static resource that may be directly referenced as analias to a memory caching node for configuration 412 retrieval. Forexample, new clients may be initialized with a hostname of theconfiguration endpoint 414. Upon instantiation of a new client, theclient may connect with the configuration endpoint 414 resolve an aliasto a memory caching node 402 and retrieve the configuration 412 from thememory caching node 402. By providing the configuration endpoint 414,clients may self-configure rather than start with a list of memorycaching nodes 402 that may become obsolete and require maintenance. Insome embodiments, a client may continue to retrieve a more currentconfiguration 412 by requesting the configuration 412 from a memorycaching node 402 referenced in the alias provided by the configurationendpoint 414 or a memory caching node 402 directly.

In one embodiment, the management system 416 assumes responsibility forthe configuration 412. In another embodiment, memory caching nodes 402may be cluster-aware such that, as new memory caching nodes 402 aredetected, they may be added to the configuration 412. In anotherembodiment, the management system 416 may store an updated configuration412 in an identified memory caching node 402, such as a memory cachingnode 402 identified by an alias maintained by the configuration endpoint414. Each memory caching nodes 402 may then monitor the identifiedmemory caching node 402 for changes and download the configuration 412when it is determined that the configuration 412 has changed. In someembodiments, the identified memory caching node 402 may distributeand/or notify other memory caching node 402 in the cache cluster 413 ofchanges to configuration 412. By obtaining an updated configuration 412,a client may adapt to dynamically changing memory caching nodes 402within the caching cluster 413.

A memory caching node 413 may follow a protocol that includes rulesgoverning cached data. In one embodiment, the rules specify cacheeviction upon a last recently used basis when the cache space 404 isfull. In another embodiment, the rules allow cached data, such as thekey-value pair 410 to be associated with a time to live after which thedata will no longer be available. In some embodiments, the protocolgoverning cached data has been extended such that configuration 412stored in the reserved configuration space 402 is not subject to therules governing cache eviction and/or time to live.

Turning now to FIG. 5, an illustrative example 500 of logicalconnections between components in accordance with at least oneembodiment is shown. A purpose of the cache clusters 513 using memorycaching nodes 510 may be to prevent a load on and/or slow response froman API or data store 514, such as a relational database, NoSQL databaseand key-value store. In the embodiment shown, an application 502 maycause a client driver 504, such as through a library API call, toretrieve a configuration 508 from a memory caching node 510 identifiedby an alias retrieved from a predetermined configuration endpoint 506.The configuration 508 may include information to enable communicationwith data store 514 and memory caching nodes 510. Upon configuring thecommunication, the client driver 504 may field requests from theapplication 502 for data within the data store 514. The client driver504 may determine a memory caching node 510 to contact to see if thedata is in the cache 512 of the memory caching node 510. If so, theclient driver 504 may return the data to the application 502. If not,the client driver may request the information from the data store 514directly. Because of the request, the data store 514 and/or the clientdriver 504 may cause the data to be stored in a cache 512 of a memorycaching node 510 for future retrieval. In some embodiments, during arequest to a memory caching node 510, the client driver 504 may checkand/or be notified that a configuration change has occurred.

In some embodiments, request forwarding may occur. For example, a clientdriver 504 may make a request for data to a first memory caching node510 that may forward the request to a second memory caching node 510. Ifthe second memory caching node 510 does not have the data requested incache 512, the second memory caching node 510 may forward the request tothe data store 514. The data store may return the requested data, eitherthrough the same path or directly to the client driver 504. An advantageof request forwarding is that the client driver 504 need not have acurrent configuration 508. However, the delays may be more significantthan direct communication with a memory caching node 510.

Turning now to FIG. 6, an illustrative chart of distributed memorycaching configuration process in accordance with at least one embodimentis shown. This process may be accomplished, in one embodiment, bycomputing resources such as those seen in FIG. 2 including application202, client driver 204, configuration endpoint 206 and memory cachingnodes 210. The configuration process may include three phases:initialization 600, use 614 and reconfiguration 622. Duringinitialization, a client driver 604 prepares to receive data from acache on behalf of an application 602 by obtaining a configuration 612.In FIG. 6, the application 602 gives the client driver 604 aconfiguration endpoint identifier 606 that identifies a configurationendpoint 610, such as by hostname, address or other identifyinginformation. The client driver 604 uses this configuration endpointidentifier 606 to resolve an alias identifying a memory caching node 620comprising the configuration 612. The client driver requests 608 theconfiguration 612 from the memory caching node 620. The memory cachingnode 620 may send the configuration 612 to the client driver 604. Theclient driver 604 may then load the configuration 612 to enablecommunications with a cache cluster 613 having memory caching nodes 620.

In some embodiments, a configuration endpoint 610 is ensured for highavailability, as new applications 602 rely on the availability of theconfiguration endpoint alias. The configuration endpoint 610 may beaccess restricted based on the request or an identifier associated withthe request, such as requesting IP address, destination IP addressand/or credentials.

In the use phase 614, the client driver 604 may act as an interfacebetween the application 602 and the cache cluster 613. In someembodiments, this interface may be done with an API and/or code library.The application 602 may send a request for data 616 that is analyzed bythe client driver 604 to determine which memory caching node 620 mayhave the requested data in its cache. The client driver 604 may thensend the request 616 for data in a format recognized by the memorycaching node 620. If the data is found within the memory caching node620, the memory caching node 620 returns the data 618 to the clientdriver 604. The client driver 604 may then return the data 618 to theapplication 602. However, if the data is not found within the memorycaching node 620, the client driver's request may fail and/or beredirected to the data store.

In some embodiments, the data in a request 616 may be serviced by morethan one memory caching node 620 in a cache cluster 613. In oneembodiment, this redundancy may be due to cached data that is expensiveto recreate. In other embodiments, this redundancy may be due toreducing a server load due to a collection of frequently accessed data.The client driver 604 may use configuration information 612, informationfrom a management system regarding cache cluster 613, request latencyfrom a memory caching node 620 and/or other information or indicators todetermine which memory caching node 620 should be contacted forredundant information. In another embodiment, a memory caching node 620is randomly selected if the data is available from two or more memorycaching nodes 620.

In the reconfiguration phase 622, the client driver 604 ensures that itsconfiguration 612 is up to date by comparing its version with a versionknown to one or more of the memory caching nodes 620. In one embodiment,a client driver 604 may periodically send a request for configuration608 to one or more memory caching nodes 620. The contacted memorycaching nodes 620 may return a stored configuration 612 which may becompared against a configuration used by the client driver 604. Inanother embodiment, the client driver may request version information ofthe configuration 612 from the memory caching node 620. The clientdriver 604 may compare the version information retrieved against versioninformation of a local configuration. If the retrieved information is anewer version, the client driver 604 may request the new version of theconfiguration 612. For example, version information may be a combinationof a serially incremented number and a timestamp. In some embodiments,the client driver may receive an indicator from a memory caching node620 that a configuration has changed during the use phase 614, such as asecondary return value.

FIG. 7 shows an illustrative example of a process 700 that may be usedto update configuration in accordance with at least one embodiment. Thisprocess may be accomplished, in one embodiment, by computing resourcessuch as those seen in FIG. 2 including application 202, client driver204, configuration endpoint 206 and memory caching nodes 210. A cachecluster may provide 702 a configuration endpoint to provide an alias toa memory caching node for configuration distribution. Upon modifying 704one or more distributed memory caching nodes, such as provisioningmemory caching nodes, de-provisioning memory caching nodes, movement ofkeys, changes to key placement or other changes affecting a clientconfiguration, a new configuration may be determined 706 based on thechanges performed. Configurations stored in memory caching nodes may beupdated 710 as well as the configuration endpoint alias updated 708, ifneeded. The update to a configuration may be a replacement,concatenation, overwrite or other modification to the configuration datastored in a memory caching node.

Some or all of the process 700 (or any other processes described herein,or variations and/or combinations thereof) may be performed under thecontrol of one or more computer systems configured with executableinstructions and may be implemented as code (e.g., executableinstructions, one or more computer programs or one or more applications)executing collectively on one or more processors, by hardware orcombinations thereof. The code may be stored on a computer-readablestorage medium, for example, in the form of a computer programcomprising a plurality of instructions executable by one or moreprocessors. The computer-readable storage medium may be non-transitory.

FIG. 8 shows an illustrative example of a process 800 that may be usedto configure a client in accordance with at least one embodiment. Thisprocess may be accomplished, in one embodiment, by computing resourcessuch as those seen in FIG. 2 including application 202, client driver204, configuration endpoint 206 and cache cluster 213. A client drivermay receive 802 initialization information regarding a configurationendpoint. Using the configuration endpoint information, the clientdriver may request 804 use an alias provided by the configurationendpoint to receive 804 memory caching node information. The clientdriver may then request 805 a current configuration from the memorycaching node. The request may include explicit or implicitidentification of the application, client and/or customer requesting theconfiguration. Explicit identification may include credentials oraccount information. Implicit identification may include origin,destination, requesting IP address, destination IP address or otherinherent characteristics of the requestor or the request. Theidentification is useful if the configuration endpoint serves multiplealiases for different distributed caching clusters. The client drivermay load 806 the configuration and service 808 application requestsuntil a configuration change is needed 810. The need for a configurationupdate may be checked periodically, noted in a return value from amemory caching node, messaged to the driver or otherwise noticed by ornotified to the driver, application or client. If needed, theconfiguration may be requested from a memory caching node.

FIG. 9 shows an illustrative example of a process 900 that may be usedto manage caching in accordance with at least one embodiment. Thisprocess may be accomplished by computing resources such as those seen inFIG. 2 including application 202, client driver 204, configurationendpoint 206 and memory caching nodes 210. A management system maymonitor memory caching nodes 902 for indicators of a problem. If aproblem is discovered 904, new memory caching nodes 906 may beprovisioned 908 and/or existing memory caching nodes to be removed 910may be de-provisioned 912. For example, problems requiring new memorycaching nodes to the cache cluster may include a growth in the need forcaching bandwidth and/or caching storage. Problems requiring the removalof memory caching nodes from the cache cluster may be the decrease inneed of caching bandwidth, failing hardware and/or caching storage. Forexample, caching may be increased during seasons of high use, such as ashopping website in December. Caching may also be decreased duringseasons of low use, such as a ski retailer commerce application insummer. Some problems may also require the provisioning of new memorycaching nodes and the removal of other memory caching nodes. This mayinclude failure of a memory caching node and/or the migration from onesize of memory caching node to another size of memory caching nodes.After provisioning and/or de-provisioning memory caching nodes, a newconfiguration may be determined 914 based at least in part on thechanges in response to the problem. The new configuration may be pushedto update 920 the memory caching nodes for storage and/or update 918 thealias used by a configuration endpoint.

Turning now to FIG. 10, an illustrative example of a process 1000 thatmay be used to manage memory caching node behavior in accordance with atleast one embodiment is shown. This process may be accomplished bycomputing resources such as those seen in FIG. 2 including application202, client driver 204, configuration endpoint 206 and memory cachingnodes 210. During the monitoring 1002 of memory caching nodes, one ormore key/value pairs are identified 1003 to make redundant. Thisredundancy may be used to distribute a high load among memory cachingnodes and/or increase durability of a cached key-value pair. A secondmemory caching node may be selected 1004 and caused to service 1006 theidentified key-value pair. The second memory caching node may beidentified by load, use patterns, durability or other attributes thatmake the memory caching node desirable. In some embodiments, importantkey-value pairs are stored on three or more memory caching nodes. Usingthe changes, a new configuration may be determined 1008. Using the newconfiguration, memory caching nodes may be updated 1010 by receiving andstoring the configuration. The configuration endpoint may also beupdated 1012 by updating its alias.

For example, durability of key-value pairs that are costly tore-calculate may be factored in a decision to make the key-value pairredundant. An algorithm running on a monitoring system within themanagement system measures frequency of access to determine whichkey-value pairs will be made redundant. Using the result of thealgorithm, the management system may cause a provisioning system todistribute the key-value pairs across two or more memory caching nodes.After distributing the key-value pairs, the management system may thenupdate a configuration and cause the configuration to be stored bymemory caching nodes that form part of a cache cluster. In someembodiments, this algorithm may be modified to weigh the costs ofkey-value pairs, such that costly and frequently accessed key-valuepairs may be made redundant. In some embodiments that require furtherredundancy, multiple configuration endpoints may be used to increasedurability.

In some embodiments, the key-value pair may be transferred rather thanmade redundant. For example, a memory caching node under load may selecta range of keys to offload to a second memory caching node. In somecases, the memory caching node under load may have to continue servicingthe range of keys until all or most of clients update theirconfiguration.

In some embodiments, configurations may be propagated between memorycaching nodes. For example, once a memory caching node receives aconfiguration, the memory caching node may attempt to distribute theconfiguration to other memory caching nodes in the configuration. Inthis way the memory caching nodes may work in using peer-to-peercommunication to propagate configuration to each memory caching node. Inone embodiment, memory caching nodes in a cache cluster may track nodeswithin the cache cluster such that changes to the cache cluster aremonitored by the memory caching nodes themselves. A memory caching nodethat notices an addition or subtraction of a memory caching node, or isthe subject of the addition or subtraction, may create a newconfiguration to distribute to the other memory caching nodes.

It should be recognized that the use of the term client driver does notnecessarily refer to software that directly supports hardware. Theclient driver is code executed by a computing resource that at leastmanages communication between an application and a distributed cachecluster. In some embodiments, this is accomplished by a library. Forexample, a developer may call functions within a library to perform thephases seen and discussed in relation to FIG. 6.

It should be recognized that the use of the term memory caching node isused as a broad term that covers more than just the specific examplesabove. Other caching types are included in this term. Other examples ofmemory caching nodes include persistent caching systems and disk cachingsystems. In one embodiment, a persistent caching system is used suchthat a cache state is saved to avoid losing the cache. In anotherembodiment, a disk caching system may be used.

FIG. 11 is an illustrative example of a mapping 1100 that may be used torepresent node locations in managed cache retrieval in accordance withat least one embodiment. This process may be accomplished by computingresources such as those seen in FIG. 2, including application 202,client driver 204, configuration endpoint 206 and memory caching nodes210. A range of possible hashes may be represented by a circle 1102.Although differences in angles may graphically show similar spacesbetween nodes, any number of hashes may be included within a range ofangles. For example, in one embodiment, there may be thousands of hashescontained within a small portion of the circle and in anotherembodiment, there may not be any hashes contained within a secondportion of the circle.

Keys Z (1110), Y (1112), X (1114) and W (1116) correspond to cachingangles measured from a reference angle 1101, such as, for example,angles 1126, 1130, 1132 and 1134, shown on circle 1102. The keys may beinput into a hashing function that returns a corresponding cachingangle. A memory caching node may be assigned at least one caching anglealong circle 1102. Larger memory caching nodes may be assigned morecaching angles, which may grant a larger coverage over the circle 1102.It is understood that the number of hashes can differ per angle. Forexample, memory caching node assignments to memory caching node Ainclude caching angle 1104 and caching angle 1106. A key is assigned toa memory caching node first encountered travelling clockwise around thecircle from a caching angle corresponding to the key. For example,caching angle 1130 determined from a hash of key Z 1110 is followedclockwise 1138 to the caching angle assignment 1 (1104) of memorycaching node A.

In FIG. 11 a caching angle is shown to be measured clockwise from thereference angle 1101. For example, caching angle 1130 may have a smallerangle than caching angle 1126 as measured from the reference angle. Todetermine which memory caching node is responsible for a key, the key isfirst processed through a hash function to determine a caching angle.The caching angle may then be followed clockwise until the first memorycaching node assignment occurs. For example, key X 1114 resolves to thecaching angle 1126 shown. The caching angle is then swept clockwisealong line 1124 until the first memory caching node assignment occurs atcaching angle 1104 which is assignment number 1 for memory caching nodeA. Therefore key X is assigned to memory caching node A. Similarly, thecaching angle of key Z (1110) sweeps 1138 to caching angle 1104 which isassignment 1 of memory caching node A. For the same reasons, Key Y 1112is assigned to memory caching node A, assignment 2 (1106) because of thesweep 1136 to the assignment of caching angle 1106. Key W 1116 isassigned to memory caching node B because sweeping 1140 clockwisearrives at the assignment of a caching angle 1108 assigned to assignment1, memory caching node B.

Memory caching node assignments may be accomplished by several differentmethods. In one embodiment, the client driver comprises code configuredto assign memory caching nodes within the mapping. In such anembodiment, the client may be aware of the angles on the mapping thatare “hot” and as such require an additional node to offload one or morerequests. In another embodiment, a management system may aid a clientdriver in assigning caching angles. For example, a management systemmonitors the access of keys and determines an optimum placement ofassignments to reduce server loads on memory caching nodes. Themanagement system may be aware of one or more aspects of the cachecluster in general as well as added nodes that it may provide as “hints”to the client driver.

In another embodiment, one or more clients monitor usage of the memorycaching nodes. If needed, a client may request provisioning of a newmemory caching node to add to the cache cluster. For example, a clientmay determine that a latency of a response from a memory caching nodehas increased beyond an acceptable threshold. As another example, theclient may query the memory caching node using a protocol extension orreviewing an access log, the client determines that one or more keys areaccessed with a frequency above a threshold. The client may then requestthat a provisioning system provision a new memory caching node. Theclient may then assign the memory caching node one or more cachingangles.

In one example, shown in FIG. 12, a memory caching node C is added tothe cache cluster illustrated in FIG. 11. Memory caching node C is ableto support three caching angles: caching angle assignment 1 (1118),caching angle assignment 2 (1120) and caching angle assignment 3 (1122).This ability to support three caching angles may be due to the size,processing ability and/or placement of memory caching node C. Further,as illustrated, nodes in the cluster may not necessarily be equidistantfrom each other in terms of the angular distances between them. Somenodes may be closer to each other than others (in terms of angulardistance in the representation in FIGS. 11-12) due to various factors inconnection with the key spaces served by the nodes. In the exampleshown, Key X 1114 and Key Z 1110 may be “hot” keys that are frequentlyaccessed (i.e., accessed with a frequency in a range designated as“hot”), therefore, causing the utilization of caching angle 1104 to beresponsible for the high utilization of memory caching node A. Amanagement system may cause a new memory caching node C to receive acaching angle assignment 2 (1120). Due to the new assignment of cachingangle 1120, Key X 1114 may now be serviced by memory caching node C, asa sweep of caching angles along line 1128 leads to caching angle 1120that is assigned to memory caching node C, assignment 2. Key Z 1110 mayremain with memory caching node A due to an assignment of caching angle1104.

In another example, an access history of Key W 1116 may be such that KeyW 1116 should be serviced by more than one memory caching node. Thisreplication of the key space may be due to load, difficulty ofcalculation of the underlying cached value or other replication need. Asshown in FIG. 12, memory caching node C, assignment 1 (1118) has beenassigned the same caching angle assignment 1118 as the caching angleassignment 1108 of memory caching node B, assignment 1 (1108). Thus,memory caching node B and memory caching node C share responsibility forthe same key space. In some embodiments, only a portion of the key spaceis noted as replicated.

In yet another example, a management system may also determine that thekey space covered by caching angle 1105 assigned to memory caching nodeB, assignment 2 should be smaller. A caching angle 1122 assignment 3 tomemory caching node C is added between assigned caching angles 1105 and1106. As may be noted in FIG. 12, the range responsibility betweencaching angles 1105 and 1122 need not be symmetric. In some cases,memory caching node C's range may be smaller than memory caching nodeA's range, but may be more frequently accessed. Considerations, such asrange and frequency of access, may be used to determine the assignmentof caching angle assignments. It should be recognized that in each ofthe above embodiments, the client driver may be in control of thedetermination of the location of the nodes and as such, the managementsystem may provide information which may be used by the client driver inmaking the determinations.

It should be recognized that while the memory caching angle assignmentshave been discussed in terms of three or less assignments, actual usemay be higher including hundreds, thousands, millions or more of cachingassignments. The few assignments shown are for simplifying discussion.

While memory caching nodes have been used for illustration of variousaspects of the present disclosure, it should be recognized that thestructures and processes described may also be more broadly applied tostorage nodes and clusters of computing resources in general. Forexample, a storage node may include a memory caching node, databases andread-replicas. In one embodiment, membership information of a cluster ofnodes is shared with clients of the nodes. For example, the processesand structures may be used in database scaling. Configuration ofread-replicas may be stored in a configuration space on a databaseserver. Clients of the database server may detect changes, such asadditions or subtractions, to the read-replicas by requesting theconfiguration from a read-replica, using client configuration updatetechniques described above. In another example, the processes andstructures may be used in database clustering. A cluster configurationmay be stored in the database itself alongside the data that makes upthe distributed data store of the cluster, which may be retrieved byclients of the database. This allows the client initialization to bedecoupled from server resources.

FIG. 13 illustrates aspects of an example environment 1300 forimplementing aspects in accordance with various embodiments. As will beappreciated, although a Web-based environment is used for purposes ofexplanation, different environments may be used, as appropriate, toimplement various embodiments. The environment includes an electronicclient device 1302, which can include any appropriate device operable tosend and receive requests, messages or information over an appropriatenetwork 1304 and convey information back to a user of the device.Examples of such client devices include personal computers, cell phones,handheld messaging devices, laptop computers, set-top boxes, personaldata assistants, electronic book readers and the like. The network caninclude any appropriate network, including an intranet, the Internet, acellular network, a local area network or any other such network orcombination thereof. Components used for such a system can depend atleast in part upon the type of network and/or environment selected.Protocols and components for communicating via such a network are wellknown and will not be discussed herein in detail. Communication over thenetwork can be enabled by wired or wireless connections and combinationsthereof. In this example, the network includes the Internet, as theenvironment includes a Web server 1306 for receiving requests andserving content in response thereto, although for other networks analternative device serving a similar purpose could be used as would beapparent to one of ordinary skill in the art.

The illustrative environment includes at least one application server1308 and a data store 1310. It should be understood that there can beseveral application servers, layers, or other elements, processes orcomponents, which may be chained or otherwise configured, which caninteract to perform tasks such as obtaining data from an appropriatedata store. As used herein the term “data store” refers to any device orcombination of devices capable of storing, accessing and retrievingdata, which may include any combination and number of data servers,databases, data storage devices and data storage media, in any standard,distributed or clustered environment. The application server can includeany appropriate hardware and software for integrating with the datastore as needed to execute aspects of one or more applications for theclient device, handling a majority of the data access and business logicfor an application. The application server provides access controlservices in cooperation with the data store, and is able to generatecontent such as text, graphics, audio and/or video to be transferred tothe user, which may be served to the user by the Web server in the formof HTML, XML or another appropriate structured language in this example.The handling of all requests and responses, as well as the delivery ofcontent between the client device 1302 and the application server 1308,can be handled by the Web server. It should be understood that the Weband application servers are not required and are merely examplecomponents, as structured code discussed herein can be executed on anyappropriate device or host machine as discussed elsewhere herein.

The data store 1310 can include several separate data tables, databasesor other data storage mechanisms and media for storing data relating toa particular aspect. For example, the data store illustrated includesmechanisms for storing production data 1312 and user information 1316,which can be used to serve content for the production side. The datastore also is shown to include a mechanism for storing log data 1314,which can be used for reporting, analysis or other such purposes. Itshould be understood that there can be many other aspects that may needto be stored in the data store, such as for page image information andto access right information, which can be stored in any of the abovelisted mechanisms as appropriate or in additional mechanisms in the datastore 1310. The data store 1310 is operable, through logic associatedtherewith, to receive instructions from the application server 1308 andobtain, update or otherwise process data in response thereto. In oneexample, a user might submit a search request for a certain type ofitem. In this case, the data store might access the user information toverify the identity of the user, and can access the catalog detailinformation to obtain information about items of that type. Theinformation then can be returned to the user, such as in a resultslisting on a Web page that the user is able to view via a browser on theuser device 1302. Information for a particular item of interest can beviewed in a dedicated page or window of the browser.

Each server typically will include an operating system that providesexecutable program instructions for the general administration andoperation of that server, and typically will include a computer-readablestorage medium (e.g., a hard disk, random access memory, read onlymemory, etc.) storing instructions that, when executed by a processor ofthe server, allow the server to perform its intended functions. Suitableimplementations for the operating system and general functionality ofthe servers are known or commercially available, and are readilyimplemented by persons having ordinary skill in the art, particularly inlight of the disclosure herein.

The environment in one embodiment is a distributed computing environmentutilizing several computer systems and components that areinterconnected via communication links, using one or more computernetworks or direct connections. However, it will be appreciated by thoseof ordinary skill in the art that such a system could operate equallywell in a system having fewer or a greater number of components than areillustrated in FIG. 13. Thus, the depiction of the system 1300 in FIG.13 should be taken as being illustrative in nature, and not limiting tothe scope of the disclosure.

The various embodiments further can be implemented in a wide variety ofoperating environments, which in some cases can include one or more usercomputers, computing devices or processing devices which can be used tooperate any of a number of applications. User or client devices caninclude any of a number of general purpose personal computers, such asdesktop or laptop computers running a standard operating system, as wellas cellular, wireless and handheld devices running mobile software andcapable of supporting a number of networking and messaging protocols.Such a system also can include a number of workstations running any of avariety of commercially-available operating systems and other knownapplications for purposes such as development and database management.These devices also can include other electronic devices, such as dummyterminals, thin-clients, gaming systems and other devices capable ofcommunicating via a network.

Most embodiments utilize at least one network that would be familiar tothose skilled in the art for supporting communications using any of avariety of commercially-available protocols, such as TCP/IP, OSI, FTP,UPnP, NFS, CIFS and AppleTalk. The network can be, for example, a localarea network, a wide-area network, a virtual private network, theInternet, an intranet, an extranet, a public switched telephone network,an infrared network, a wireless network and any combination thereof.

In embodiments utilizing a Web server, the Web server can run any of avariety of server or mid-tier applications, including HTTP servers, FTPservers, CGI servers, data servers, Java servers and businessapplication servers. The server(s) also may be capable of executingprograms or scripts in response requests from user devices, such as byexecuting one or more Web applications that may be implemented as one ormore scripts or programs written in any programming language, such asJava®, C, C# or C++, or any scripting language, such as Perl, Python orTCL, as well as combinations thereof. The server(s) may also includedatabase servers, including without limitation those commerciallyavailable from Oracle®, Microsoft®, Sybase® and IBM®.

The environment can include a variety of data stores and other memoryand storage media as discussed above. These can reside in a variety oflocations, such as on a storage medium local to (and/or resident in) oneor more of the computers or remote from any or all of the computersacross the network. In a particular set of embodiments, the informationmay reside in a storage-area network (“SAN”) familiar to those skilledin the art. Similarly, any necessary files for performing the functionsattributed to the computers, servers or other network devices may bestored locally and/or remotely, as appropriate. Where a system includescomputerized devices, each such device can include hardware elementsthat may be electrically coupled via a bus, the elements including, forexample, at least one central processing unit (CPU), at least one inputdevice (e.g., a mouse, keyboard, controller, touch screen or keypad),and at least one output device (e.g., a display device, printer orspeaker). Such a system may also include one or more storage devices,such as disk drives, optical storage devices, and solid-state storagedevices such as random access memory (“RAM”) or read-only memory(“ROM”), as well as removable media devices, memory cards, flash cards,etc.

Such devices also can include a computer-readable storage media reader,a communications device (e.g., a modem, a network card (wireless orwired), an infrared communication device, etc.) and working memory asdescribed above. The computer-readable storage media reader can beconnected with, or configured to receive, a computer-readable storagemedium, representing remote, local, fixed and/or removable storagedevices as well as storage media for temporarily and/or more permanentlycontaining, storing, transmitting and retrieving computer-readableinformation. The system and various devices also typically will includea number of software applications, modules, services or other elementslocated within at least one working memory device, including anoperating system and application programs, such as a client applicationor Web browser. It should be appreciated that alternate embodiments mayhave numerous variations from that described above. For example,customized hardware might also be used and/or particular elements mightbe implemented in hardware, software (including portable software, suchas applets) or both. Further, connection to other computing devices suchas network input/output devices may be employed.

Storage media and computer readable media for containing code, orportions of code, can include any appropriate media known or used in theart, including storage media and communication media, such as but notlimited to volatile and non-volatile, removable and non-removable mediaimplemented in any method or technology for storage and/or transmissionof information such as computer readable instructions, data structures,program modules or other data, including RAM, ROM, EEPROM, flash memoryor other memory technology, CD-ROM, digital versatile disk (DVD) orother optical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices or any other medium which canbe used to store the desired information and which can be accessed bythe a system device. Based on the disclosure and teachings providedherein, a person of ordinary skill in the art will appreciate other waysand/or methods to implement the various embodiments.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the claims.

Other variations are within the spirit of the present disclosure. Thus,while the disclosed techniques are susceptible to various modificationsand alternative constructions, certain illustrated embodiments thereofare shown in the drawings and have been described above in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructionsand equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed embodiments (especially in thecontext of the following claims) are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected” is to be construed as partly or wholly contained within,attached to, or joined together, even if there is something intervening.Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate embodiments of the invention anddoes not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this disclosure are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications and patents,cited herein are hereby incorporated by reference to the same extent asif each reference were individually and specifically indicated to beincorporated by reference and were set forth in its entirety herein.

What is claimed is:
 1. A computer-implemented method, comprising:requesting, by a client device from a static configuration endpoint of acache cluster, a configuration of the cache cluster, the cache clustercomprising a set of memory caching nodes that each comprise a reservedmemory space that is configured to store the configuration, the reservedmemory space being exempt from one or more rules of a caching protocol,the static configuration endpoint being configured to resolve a locationof the configuration within the reserved memory space of a memorycaching node; receiving the configuration from the memory caching nodeof the cache cluster; transmitting, by the client device, a cachingrequest utilizing the caching protocol and the configuration;determining, by the client device, that a latency of a responsecorresponding to the caching request exceeds a threshold value;transmitting, utilizing an extension of the caching protocol, aprovisioning request for a new memory caching node to be added to thecache cluster, the new memory caching node being provisioned to thecache cluster based at least in part on transmission of the provisioningrequest; and receiving, by the client device, an updated configurationof the cache cluster identifying at least an addition of the new memorycaching node to the cache cluster.
 2. The computer-implemented method ofclaim 1, further comprising: defining a key space for each memorycaching node in the set of memory caching nodes, the key space beingdefined by determining one or more caching angles to assign to eachmemory caching node in the set of memory caching nodes; and requesting,by the client device utilizing the caching protocol, a first set ofvalues corresponding to a first set of keys from the cache cluster usingthe key space to determine a particular memory caching node to contactfor each key of the first set of keys.
 3. The computer-implementedmethod of claim 2, wherein defining the key space for each memorycaching node in the set of memory caching nodes further comprisesdefining a hash function to be used with keys stored in the cachecluster.
 4. The computer-implemented method of claim 1, furthercomprising: defining a revised key space for each memory caching node inthe set of memory caching nodes in the cache cluster affected by theupdated configuration; and requesting a second set of valuescorresponding to a second set of keys from the cache cluster using therevised key space to determine a particular memory caching node tocontact for each key of the second set of keys.
 5. Thecomputer-implemented method of claim 1, further comprising: resolving analias provided by the static configuration endpoint to the memorycaching node; and in response to resolving the alias, requesting aconfiguration from the memory caching node.
 6. The computer-implementedmethod of claim 1, wherein the updated configuration is received from adifferent memory caching node of the cache cluster from the memorycaching node.
 7. A system, comprising: one or more computing resourceshaving one or more processors and one or more memories includingexecutable instructions that, when executed by the one or moreprocessors, cause the one or more processors to: receive, from a staticconfiguration endpoint of a cache cluster, a configuration describing aset of storage nodes in the cache cluster, the set of storage nodesindividually comprising a reserved memory space that stores a currentconfiguration of the cache cluster, the reserved memory space beingexempt from one or more rules of a caching protocol, the staticconfiguration endpoint being configured to resolve a location of theconfiguration within the reserved memory space of a storage node;determine that particular data of the set of storage nodes is accessedwith a frequency above a threshold; transmit, utilizing an extension ofthe caching protocol, a provisioning request for a new storage node tobe added to the cache cluster, the new storage node being provisioned tothe cache cluster based at least in part on transmission of theprovisioning request; and receive an updated configuration describingthe set of storage nodes in the cache cluster, the set of storage nodescomprising the new storage node.
 8. The system of claim 7, whereinexecuting the executable instructions further causes the one or moreprocessors to send a request to the storage node to retrieve an updatedconfiguration from a reserved configuration space in the storage node,the request utilizing the caching protocol.
 9. The system of claim 7,wherein executing the executable instructions further causes the one ormore processors to: request an additional configuration from a differentstorage node of the cache cluster; compare the additional configurationto the update configuration; and utilize the additional configuration insubsequent caching requests when the additional configuration isassociated with a more-recent time than a time associated with theupdated configuration.
 10. The system of claim 7, wherein executing theexecutable instructions further causes the one or more processors toassign the new storage node a portion of a hashing function result. 11.The system of claim 7, wherein executing the executable instructionsfurther causes the one or more processors to: define a key space foreach storage node in the set of storage nodes in the cache clusteraffected by the updated configuration; determine, from the updatedconfiguration, that a particular storage node is no longer included inthe configuration; and revise the key space according to a determinationthat the particular storage node is no longer included in theconfiguration.
 12. The system of claim 7, wherein the set of storagenodes comprise random access memory to hold cached data from a database.13. The system of claim 12, wherein the database provides requested datawhen the cache cluster does not contain the requested data.
 14. One ormore non-transitory computer-readable storage media having collectivelystored thereon executable instructions that, when executed by one ormore processors of a client device, cause the client device to at least:request, from a static configuration endpoint of a cache cluster, aconfiguration of the cache cluster, the cache cluster comprising a setof memory caching nodes that each comprise a reserved memory space thatstores the configuration, the reserved memory space being exempt fromone or more rules of a caching protocol, the static configurationendpoint being configured to resolve a location of the configurationwithin the reserved memory space of a memory caching node; receive theconfiguration from the memory caching node of the cache cluster; monitorresponses from the cache cluster; determine that a latency of theresponses exceeds a threshold value; transmit, utilizing an extension ofthe caching protocol, a provisioning request for a new memory cachingnode to be added to the cache cluster, the new memory caching node beingprovisioned to the cache cluster based at least in part on transmissionof the provisioning request; and receive an updated configuration of thecache cluster identifying at least an addition of the new memory cachingnode to the cache cluster.
 15. The one or more non-transitorycomputer-readable storage media of claim 14, wherein the client deviceis associated with a first network that is different from a secondnetwork associated with the cache cluster.
 16. The one or morenon-transitory computer-readable storage media of claim 14, includingfurther instructions that cause the client device to: determine a firstassignment of results of a hashing function to the set of memory cachingnodes based at least in part on the configuration; and determine asecond assignment of results of the hashing function to the set ofmemory caching nodes based at least in part on the updatedconfiguration.
 17. The one or more non-transitory computer-readablestorage media of claim 14, including further instructions that cause theclient device to periodically request a stored configuration utilizingthe static configuration endpoint.
 18. The one or more non-transitorycomputer-readable storage media of claim 14, wherein the updatedconfiguration is received by the memory caching node.
 19. The one ormore non-transitory computer-readable storage media of claim 14,including further instructions that cause the client device to: access,utilizing the extension of the caching protocol, a plurality ofconfigurations of the cache cluster, the plurality of configurationsbeing stored in a plurality of memory caching nodes of the cachecluster; determine a newest configuration from the plurality ofconfigurations; determining that the updated configuration differs fromthe newest configuration; and replacing the updated configuration withthe newest configuration based at least in part on determining that theupdated configuration differs from the newest configuration.
 20. The oneor more non-transitory computer-readable storage media of claim 14,wherein the caching protocol comprises a memcached protocol.